In manufacturing electronic devices, the first region of silicon oxide is selectively etched with respect to the second region of silicon nitride. In this etching process, a plasma of a processing gas containing a fluorocarbon gas, argon gas and oxygen gas is generated in a processing chamber of a plasma processing apparatus, as disclosed in, e.g., Japanese Patent Application Publication No. 2002-25979.
A SAC (Self-Aligned Contact) technique is known as a technique for selectively etching the first region with respect to the second region. In the SAC technique, the first region in a recess formed by the second region is etched in a self-aligned manner. In the SAC technique, the aforementioned processing gas is used and a plasma of the processing gas is generated in the processing chamber.
In the above-described technique, the second region is considerably etched when the first region is etched. Therefore, it is required to etch the first region of silicon oxide while suppressing etching of the second region of silicon nitride.